Collision boxes of different stuff

hey there,

just collected a lot of grass and wanted to build a little 'thing' out of it - whatever it will look like lol - but then I noticed, that it has no collision box - will say: It's phantom, you can walk through it.
Perhaps this has an idea behind and therefore neccessary, but if not: Please make those bundles of whatever - branches, twigs, grass - physical and not phantom.
It would be very nice to be able to build something out of them.